In metalworking and/or testing operations, particularly gear manufacturing and testing, where a workpiece is machined, equipment of some type is necessary to hold the workpiece in position in a machine tool so the machining and/or testing process can be successfully carried out. This type of equipment is known as “workholding” equipment. In the production of toothed articles, such as gears, workholding equipment can be generally categorized as two types, chucks and arbors.
Chucks hold a workpiece by contracting a component called a “collet” around the workpiece or a component thereof. For example, when a bevel or hypoid pinion with integral shaft is placed in a chuck, it is usually the shaft that is gripped by the collet which has been reduced in diameter to grip the shaft to hold the pinion in position. Examples of chucks for gripping pinion shanks can be found in U.S. Pat. No. 3,083,976 to Stark; U.S. Pat. No. 3,244,427 to Taschl; or U.S. Pat. No. 6,260,855 to Curtis.
Arbors grip a workpiece by expanding a collet into contact with a surface of the workpiece. As an example, a bevel ring gear is placed on an arbor and the collet is expanded until contact of sufficient force is established with the surface of the bore of the ring gear to hold the ring gear in position during machining. An example of an arbor for a ring gear can be found in U.S. Pat. No. 3,735,994 to Jaehn. An arbor for expanding into contact with the bore of a pinion can be found in U.S. Pat. No. 3,517,939 to Jaehn.
In either chucks or arbors, the force necessary to contract or expand the collet mechanism is provided by a draw rod in the machine tool. The draw rod is advanced and/or retracted usually via a hydraulically operated piston or sleeve attached to an end of the draw rod opposite the end communicating with the workholding mechanism. In general, movement of the draw rod in the axial direction of the chuck or arbor usually causes opposed angled surfaces of components within the workholding equipment to slide relative to one another resulting in inward (contracting) or outward (expanding) movement of the collet as is necessary to grip or release a respective workpiece or component part thereof. Generally, one angled surface is found on the collet and the other angled surface is found on an actuator attached to the draw rod or on the draw rod itself.
At times, it may be necessary to adjust the position of the draw rod in the direction of the workpiece axis such as, for example, when a workpiece of different geometry is machined, workholding equipment of a different design or dimensions is installed or a different machining tool is utilized. Draw rods are commonly positioned via a nut that is turned in one direction or another on a threaded end portion of the draw rod to axially locate the draw rod at a desired position. Known solutions typically employ a double nut, a first nut part that controls draw rod positioning, and a second nut part that traps or jams against the first to prevent it from loosening or moving. Typically two wrenches are required to adjust such an apparatus and it can be susceptible to loosening over time.
An object of the present invention is the accurate, quick adjustment without tools of machine draw rod positions for proper operation of workholding fixtures. The inventive apparatus applies to gear-production machinery such as testers, lappers, cutting and grinding machines, as well as to any machine that uses draw-rod-operated workholding fixtures. Use of this device saves cycle time for tooling changeovers, allows controlled draw-rod adjustments in fine increments, enables gross adjustments and/or exchange of a draw rod, and cannot come loose during operation.